A known vehicle seat device is disclosed in JP2009-201663A. The seat device disclosed in JP2009-201663A is provided with a pair of known type of recliners on a shoulder belt anchor side of a seatback, the side where a larger force of impact is applied, for example, during a vehicle collision, to enhance strength of the seatback against the applied large force of impact. The recliners are drivingly connected to a drive source (an electric motor) so that a driving power from the drive source may rotate a lower arm and an upper arm, which are connected to the recliner, with respect to each other. A lower side frame, which forms a framework of the seat cushion, retains the lower arm and an upper side frame, which forms a framework of the seatback, and retains the upper arm, so that an inclination angle of the seatback with respect to the seat cushion is changed.
In general, a vehicle seat device similar to the disclosed vehicle seat device uses an electric motor with a constant driving speed as the drive source. The driving speed is considered appropriate for a fine adjustment of the inclination angle of the seatback relative to the seat cushion. However, the driving speed is considered slow, for example, when tilting the seatback forward, the seatback which serves as a partition between a front seat and a back seat, to a large degree so that a passenger in the back seat may egress a vehicle from the door installed on a frontward position of the vehicle.
A need thus exists for a vehicle seat device, which is not susceptible to the drawback mentioned above.